Ethylene-Vinyl Acetal Interlayer Creep Resistance
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Solution Overview
Problem
Conventional laminated glass interlayers face challenges with heat resistance and creep issues at elevated temperatures, particularly above 50°C, due to the use of vinyl butyral resin and ionomer resins, which require high plasticizer content, leading to reduced heat resistance and increased production costs.
Innovation Solution
A glass laminate with an ethylene-vinyl acetal resin composition, comprising 80% modified vinyl acetal resin with 25-60 mol% ethylene units and 24-71 mol% vinyl alcohol units, and an acetalization degree of 5-40 mol%, minimizing plasticizer use to achieve improved flexural strength, stiffness, and creep resistance at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a large amount of plasticizer is blended into vinyl butyral resin to improve shaping workability, then molding processability is improved, but heat resistance is lowered
Solution Approach 1:
The patent changes the chemical composition parameters of the interlayer by using ethylene-vinyl acetal resin with specific acetalization degrees (5-40 mol%) and ethylene content (25-60 mol%), replacing the conventional vinyl butyral resin system. This parameter change allows achieving both good shaping workability and high heat resistance without requiring large amounts of plasticizer.
Solution Approach 2:
The patent employs a composite resin system combining ethylene-vinyl acetal resin with specific proportions (80% by mass modified vinyl acetal resin) to create an interlayer that integrates both processability and thermal stability properties, resolving the contradiction between molding ease and heat resistance.
2Temperature
If the amount of liquid plasticizer is reduced or not blended to improve heat resistance, then heat resistance is improved, but shaping temperature must be increased which increases color
Solution Approach 1:
The patent modifies the resin's chemical structure through controlled acetalization (5-40 mol%) and ethylene content (25-60 mol%), which fundamentally changes the material's thermal and rheological properties. This allows the resin to maintain good processability at lower temperatures while achieving superior heat resistance, avoiding the coloration issue.
3Strength
If ionomer resin is used to improve impact resistance and penetration resistance, then mechanical performance is improved, but whitening occurs when cooling rate is not controlled which decreases transparency
Solution Approach 1:
The patent uses ethylene-vinyl acetal resin with specifically controlled acetalization degree (5-40 mol%) and ethylene content (25-60 mol%), which provides inherent flexibility and impact resistance without the whitening problem. The resin's molecular structure allows better stress distribution during cooling, eliminating the need for strict cooling rate control.
4Ease of manufacture
If conventional vinyl butyral resin with high plasticizer content is used to improve shaping workability, then molding processability is improved, but creep resistance at elevated temperature is reduced
Solution Approach 1:
The patent creates a composite interlayer system using ethylene-vinyl acetal resin with optimized composition (80% modified vinyl acetal resin, specific acetalization degree and ethylene content ranges) that inherently provides both shaping workability and high-temperature creep resistance, eliminating the trade-off between processability and reliability.
Data Source
AI summary
This invention relates to a glass laminate containing an interlayer based on a specified ethylene vinyl acetate-based resin composition, which is particularly suitable for higher temperature applications where polymer creep can be an issue, such as overhead architectural glazing, spandrels and bolted laminate applications, and particularly for locations where the glazing temperature can exceed 50° C., and even 60° C., for an extended period.